1. Field of the Invention
The present invention relates to an electrostatic recording apparatus of electrophotographic type, and more particularly to an electrostatic recording apparatus using a photoconductor drum having photoconductor sheet wound on a drum surface and a managing system therefor.
2. Description of the Related Art
In an electrostatic recording apparatus, in general, a photoconductor sheet is charged with electricity through an exposure of an optical image to produce an electrostatic latent image, which is then developed to obtain a toner image on the photoconductor sheet. Thereafter, the toner image is transferred onto a sheet of paper to be fixed on the sheet, thereby achieving a recording operation. In this process, the amount of electricity charged on the photoconductor sheet, namely, the level of an electric potential of the photoconductor sheet determines the effect of the electrostatic recording process, and hence there is disposed a control mechanism associated therewith.
There has been filed a Japanese patent application (JP-B-61-56514 corresponding to JP-A-54-37760) in which a portion of a photoconductor sheet is wound on a drum such that a utilized portion of the photoconductor sheet is changed by winding up the sheet. In such a photoconductor sheet of the winding type, a cap portion of an opening disposed on the drum to pass the photoconductor sheet in the forward and backward directions is set to a ground potential in any situation or the cap potential is set to the ground potential when the cap portion is located at a position opposing to surface potential detector. An object of this system is that a zero potential correction is conducted on the surface potential detector when the cap portion passes under the surface potential detector. Another object thereof is to measure the surface potential of the photoconductor sheet by the surface potential detector so as to control a charging device or charger. In either case, the potential of the cap portion is open or is set to the ground potential.
On the other hand, the JP-A-58-4172 describes a system in which when the cap portion is set to a location opposing to the surface potential detector, a calibration voltage is connected to the cap portion so that the surface potential detector is calibrated, or the cap portion is connected to an ammeter to measure a corona current so as to adjust an output from the power source for the charging device.
According to the technique described above, the cap portion (reference potential measured section) disposed in a portion of the surface of the photoconductor sheet is employed as an electrode to calibrate the surface potential detector or as an electrode to detect the corona current of the charging device.
A conventional technique concerning an electrostatic recording apparatus using a photoconductor drum having a photoconductor sheet wound on the surface is disclosed in JP-A-49-40737. This conventional technique concerns an electrostatic recording apparatus using a photoconductor sheet wound drum, in which a photoconductor sheet is drawn out from a stock roll accommodated in the drum, to the outside of the drum via an opening formed in part of the drum, to be wound on the surface of the drum and is then taken in the drum through the opening again to be wound by a take-up roll. A metal portion of a drum cap of a normal development type copying machine is connected to a ground potential and has a surface on which high resistive film such as aluminum oxidized film is formed so that toner is not attached on the surface of the drum cap.
Further, a technique concerning the electrostatic recording apparatus of this type is disclosed in JP-A-2-139583, proposed by inventors including one of the inventors of the present invention. In this technique, a drum cap is utilized to measure a surface potential of a photoconductor on a photoconductor drum.